Pollination effectiveness in a generalist plant: adding the genetic component

Abstract

Summary The pollination effectiveness of a flower visitor has traditionally been measured as the product of a quantity component that depends on the frequency of interaction and a quality component that measures the per‐visit effects on plant reproduction. We propose that this could be complemented with a genetic component informing about each pollinator's contribution to the genetic diversity and composition of the plant progeny. We measured the quantity and quality components of effectiveness of most pollinator functional groups of the generalist herb Erysimum mediohispanicum. We used 10 microsatellite markers to calculate the genetic component as the diversity of sires among siblings and included it into the calculation of the pollination effectiveness. Functional groups varied in the quantity and quality components, which were shown to be decoupled. Functional groups also differed in the genetic component. This component changed the estimates of pollination effectiveness, increasing the differences between some functional groups and modifying the pollination effectiveness landscape. We demonstrate that including the genetic component in the calculation of the pollination effectiveness may allow a more complete quantification of the contribution of each pollinator to the reproductive success of a plant, providing information on its mating patterns and long‐term fitness.

The Landscape Genetic Signature of Pollination by Trapliners: Evidence From the Tropical Herb, Heliconia tortuosa

“…Although H. tortuosa is visited by multiple species of hummingbirds, our study suggests that this pollination network has high cryptic specialization (Fenster et al, 2004), where successful pollination largely comes from the few traplining hummingbird species. A reduction in the number of realized pollinators has been reported in other species of plants that are visited by multiple functional groups of pollinators (Watts et al, 2012; Rhodes et al, 2017; Valverde et al, 2019; Temeles et al, 2019). Therefore, our results support a growing body of work showing that the total number of floral visitors is neither a good predictor nor any guarantee of effective pollen transfer, especially in the Anthropocene where habitat loss and fragmentation are expected to continue (Defries et al, 2010; Hansen et al, 2013).…”

“…Our results are consistent with other studies that examined how pollinator functional traits (body morphology, body size, foraging strategy) influence pollination success. In other systems, high morphological affinity between floral structures and pollinator characteristics have been reported to facilitate flower handling (Maglianesi et al, 2014), increase pollen removal (Watts et al, 2012; Rhodes et al, 2017; Temeles et al, 2019), and enhance the genetic diversity of sired seeds (Valverde et al, 2019). In H. tortuosa , flower morphology is closely matched by the long and curved bills of traplining hummingbirds.…”

“…Additionally, territorial hummingbirds will most likely transfer pollen locally, thereby increasing the differentiation of pollen pools sampled among forest fragments ( Figure 2D ). This study thus adds to our understanding of how different pollinator functional traits influence patterns of contemporary pollen flow (see Krauss et al, 2017; Rhodes et al, 2017; Castilla et al, 2017; O’Connell et al, 2018; Brunet et al, 2019; Valverde et al, 2019). To our knowledge, this is the first study that assesses the landscape genetic signature of different pollinator foraging strategies by comparing the differentiation of pollen pools sampled at the local and landscape scale.…”

Pollinator effectiveness in a composite: a specialist bee pollinates more florets but does not move pollen farther than other visitors

“…Thus, our estimates of effective pollen movements likely reflect true pollen transport distances, regardless of compatibility. In other forb species, pollen transport distances are much shorter than 16 m (Evans et al., ; Thavornkanlapachai et al., ; Valverde et al., ), with pollen sometimes moving <1 m between mates (Evans et al., , Valverde et al., ).…”

Different Pollinators’ Functional Traits Can Explain Pollen Load in Two Solitary Oil-Collecting Bees

“…However, visit frequency or total body size cannot totally explain pollen load size, since larger pollinator species often make brief visits, decreasing the probability of pollen collection; thus, in such cases, other features could be more relevant to the amount of pollen extracted. For example, a study of Eurysimum mediohispanicum populations [ 10 ] found that large bees make short visits, but they handle the flower very quickly and with great accuracy, thereby increasing their total pollen load. In this sense, the pollinators’ handling abilities could be a key factor in improving the amount of pollen extracted per visit, since staying longer can increase the probability of them extracting more grains per visit [ 11 ].…”